help about replacing cars.

hello everyone.
?need some help..i replaced cheetah by agera one..i just renamed the agera file to cheetah and put them to x64e.rpf>levels>gta5>vehicles.rpf/...2 .ytf file and two .ytd file...it worked for me..but the problem is some structure of the new car is still of the cheetah like the bumper,spoiler and the main one is the new car's front is old car's back....though i removed some part by los santo but the exhaust of the new car and the exhaust of the old is not same...so when it fires up,,the fire of exhaust came from the old cheetah's ehaust remaining in the new car design,,there are some meta files included with the agera one's mod file like vehicle.meta,carclos,handeling,vehicles,carvariation,direcx.meta...but i dont know where to put them..can you give me a solution????